The purpose of this project is to study the biosynthesis and function of a junction protein found only in the eye lens - MP26. Using a previously characterized bovine MP26 cDNA as a probe, full-length clones coding for MP26 will be isolated from Xenopus, mouse, and chicken lens cDNA libraries. The developmental expression of MP26 and its relationship to crystallin synthesis will be examined both at the RNA and protein level. A co-culture system consisting of A9 cells and LMTK cells transformed with MP26 cDNA will be used as a model for studying communication between cells and the role of different regions of MP26 in the functioning of the lens junction. The latter aim will be accomplished by mutagenesis of the cDNA. A rat genomic MP26 gene will be characterized and used to study the regulation of MP26 biosynthesis. An embryonic lens epithelium cell culture system will be used as an in vitro model for lens differentiation and for determining the sequences involved in regulation of the MP26 gene. A long-term goal of this project is to isolate and characterize the factors involved in lens specificity of the MP26 gene. An antisense RNA producing vector will be injected into Xenopus eggs in order to block the synthesis of MP26. This may provide an understanding for the role of the MP26 in the development of the lens. Furthermore, by using an inducible vector system for production of antisense RNA, the role of MP26 in lens induction at different periods of development will be examined. This reverse genetic system will be used as a model for future studies involving the role of junctional communication as well as crystalins in other vertebrates and their role in cataract formation.